Matthew Franck in NRO:

Can the president, as Rivkin and Gray suggest, simply issue an executive order adding a citizenship question to the census in order to “comply with the requirements of Section 2”? Not, I should think, if the Congress has not asked for the pertinent information on male citizens over 21 denied the vote, in order to set in motion a reduction of offending states’ congressional representation. And no enforcement legislation exists requiring any such information.
A little over a week ago, Chief Justice Roberts rejected the Trump administration’s stated reason for the citizenship question as pretextual. Whether that decision was right or wrong, the Rivkin-Gray gambit looks like a dubious new pretext for adding a citizenship question to the census.